Studs and studded shoes, such as shoes used in football, are commonly used to provide a good grip and traction on soft ground, such as turf. For example, studded shoes comprise studs which can penetrate the ground and prevent the studded shoe from sliding above the ground.
In football and other sports, the soil conditions of the respective playing fields may vary. This variation may be due to external influences, such as rain, whereby the ground is softened. On the other hand, the ground may be very dry and hard. Variations in surface conditions may also be present across different sections of a field. These variations may include small bumps or even larger depressions.
Therefore different types of studs and studded shoes have been developed. The studs typically have a rotationally-symmetric shape but may also have different shapes, such as a triangular or elongated shape. The stud shape allows for quick changes of speed or direction, as typically occurs in football and many other sports.
In the past, studs or studded shoes have been developed in order to provide an improved power transmission or to provide an ability to adapt to different ground conditions. For example, International Publication No. WO 03/071893 discloses a studded shoe in which several studs are connected via springs. For example, FIG. 3a shows that a larger stud may penetrate soft ground and no force is transmitted via the springs to other studs connected with the first stud. On the other hand, FIG. 3b shows that on hard ground the stud is pushed into the direction of the sole, so that the springs transmit a force to the smaller studs, which are then pushed away in order to improve the grip with the ground.
Great Britain Publication No. 2425706 A discloses a football shoe comprising a sole with studs, which may move independently from each other in the forefoot area of the sole. In this example, the studs are attached to segmented elements. See FIG. 3. The segmented elements are attached to an elastic layer of the sole which may stretch under pressure, thus allowing the studs to move. Similarly, U.S. Pat. No. 5,384,973 discloses a sole with spikes wherein single segments of the sole are separated, allowing for an independent movement of the segments. See FIG. 27.
U.S. Pat. No. 3,593,436 discloses a sole for a sports shoe, which is manufactured from a single piece of an elastic material. The sole comprises a plurality of studs that extend downwards from the sole. The disclosed shoe is useful for providing a good grip on synthetic turf, which does not damage the turf.
German Patent No. 298 07 086 U1 relates to a stud that comprises a movable core. In this example, the movable core is built into the stud and may be pushed outwards via a spring. Thus, depending on the properties of the ground, the stud may enter the ground.
European Patent No. 1 857 006 A1 relates to situations where the force exerted onto individual studs leads to deformation of the sole, which may be uncomfortable to the athlete wearing the shoe. The discomfort experienced by the athlete may be reduced by grouping several studs, which avoids movement of a single stud. The problem of cushioning forces in axial direction is also addressed in German Patent No. 41 23 302, which teaches the use of a cushioning hook element to increase the comfort of the athlete.
German Patent No. 2 313 646 also addresses this problem via use of a stud having a holding element and a supporting element. An intermediate element is attached between these elements, which supports elastic movement of the supporting element in the supporting direction.
European Patent No. 0 356 637 B1 is also directed to improving the cushioning of sports shoes having a sole with studs. In this example, angular bodies are attached to the studs, which may lead to deformation and, thus, cushioning under non-axial forces.
U.S. Pat. No. 5,505,012 discloses the use of so-called bumpers, which are used to attach the studs to the sole as a way of reducing the force between the sole and the studs.
German Patent No. 196 52 462 A1 relates to a sole with different zones of rigidity, which may improve rolling-off of the foot.
U.S. Pat. No. 5,617,653 relates to attaching studs to sports shoes. In this example, when a certain force is exceeded, the studs may be released from the shoe in order to prevent injuries.
German Patent No. 34 33 337 A1 is directed to a system of two studs, which serve to improve the wearing comfort.
The prior art, however, does not provide a solution that provides both improved traction and flexibility. For example, the attachment of studs to the sole leads to an increased rigidity of the sole in the area of the attachment, which is especially true for studs that are not rotationally-symmetric. Such studs may be better suited than rotationally-symmetric studs for quick changes of direction, but asymmetric studs generally have a larger attachment area that considerably increases the rigidity of the sole in that area. As a result, in many cases, studs are not attached to the shoe in the bending area of the shoe The absence of studs in the bending area increases flexibility and improved wearing comfort, but reduces grip.
In other cases, studs are attached to the bending area for an improved grip, which in turn reduces flexibility. This configuration reduces wearing comfort and may also lead to reduced traction since the foot cannot be rolled-off optimally. Hence, known studded shoes are generally built to provide good traction, which results in reduced flexibility of the shoe in the bending area. As a result, movements such as acceleration as required in sports such as football become more difficult for an athlete.
The technical problem underlying the present invention is therefore to provide a stud, a shoe sole, and a studded shoe that at least partially overcomes the disadvantages of the prior art so that good traction and improved flexibility of the sole are possible.